Well, I have to admit that I’m really getting into the whole world-building thing. Still, you may be right about getting ahead of myself. I guess I was thinking that the more prep I can do before we start playing, the better, but it does make sense to at least make sure I’m prepping something people want to play with.
I need to mention that I am jealous of the role playing teacher. 
Glee, that’s awesome!
I haven’t posted much on these boards but I do consider myself a subject matter expert on RPGs? Why? Well, I have been playing them for twenty nine years, with twenty four of those years serving as DM/GM. While most of my experience is with DND, I have run Vampire (old and new), Alternity, and some others, and have read many, many more. I am still learning! But I have picked up some tricks along the way.
I agree that you need to talk to your players. What kind of game do they want? You said that you want a low magic campaign. Do they? Or do they want to blow things up left and right with magic? Essentially, what is the tone and style of the game? And it will help if you are on the same page as your players on this one.
To that end, the various flavors of DND (I divide them as 1/2E, 3E and 4E) can help with most flavors but they will do so in different ways. DND in 1/2E and 3E plays very differently at low (1-5) level than it does at mid (6-10) or high (11-15 for 3E, 11+ for 1/2E) or epic (16+ for 3E). Essentially, if the decision is to play low magic, keeping the levels below level five will work for most versions of DND. However, as others have mentioned as well, when you get above that level, DND changes in its tone.
Once the tone and style of the game is decided, then you get to the characters. I usually ask that the players create a party, not individual characters but give me a party that will work together and stay together. My rule is that if a character doesn’t have a reason for staying with the group, then that player writes up a new character that will stay with the group. It’s one of the few things I assign to players, in that they must keep their party together. I will help, certainly, but most of it is up to them.
By this point, you should have a good idea of what the players want to do with their characters. Do they want to kill things and take its treasure? Do they want a political game? Do they want to explore ruins of ages past? Do they want to create their own kingdom? If they don’t know, encourage them to think about it and ask them these questions occassionally to see if they have an answer.
Once that is done, then you can figure out where to put them in your world. Do you have a place with old ruins they could explore? What about bandits on the roads for some excitement? Is there open area if they want to retire their characters as dukes or kings? Is that possible? Should it be? What kingdoms need diplomats for a more political game? Can you advise them on these things during character creation so they have characters that fit their goals?
When it comes to world building, having the big picture is great and I highly recommend it. Once that is done, only create what you need for the next game or two. There’s nothing worse than spending time preparing for something in the west and then they decide to go east! (Yes, you can guide them to your adventure to some extent. My own personal style has been to allow them to go where ever and I usually have ideas on it but I do try and “nudge” them the way I prepared.) So, figure out the town or village where they are based, the NPCs with whom they will interact (maybe mayor, innkeep, storekeep, guild members, and the like) and have those ready. Then, create the dungeon or whatever conflict for next time. Maybe have a few contingencies that could go anywhere, in case they go off your map.
So, that’s my advice at this point. I could examine DND if you need some pointers on that if you need questions answered on a particular edition. (I have played 'em all!) I am sure I will post more as I think about it!
I hope this helped and I hope you come back and let us know how it’s going!
Thanks!
vislor
Well, I’m not saying that you should ditch everything you worked on so far, but I strongly suggest you talk to your players before getting too deeply invested. Even if you created something that your players aren’t too keen about, chances are you can recycle most of what you already built.
In my time as DM I maybe built two worlds in total. Both those worlds were eventually abandoned, as I noticed that I didn’t keep my players wishes in regard when building. Also, you can make it really complicated with all kinds of new races (or worse: new traits for existing races) but chances are, your players have some idea of a world already after they read the PHB. And the world in the PHB is very different from what you are coming up with.
Since you are just starting out as GM, I strongly suggest you first do some standard adventures with your group. Build a track record as a DM, familiarize yourself with the different aspects of the game, the different classes and races, skills and feats, prestige classes. Then, when you can instantly tell the maximum amounts of attacks of opportunity per round a rogue with Dex 16 and combat reflexes gets, you are ready to build your own world. You know which game mechanics to change, and which to leave in, etc. But most importantly, you know why you change them.
It’s much worse than you think. 
I actually teach chess, roleplaying and computer games full-time. 
It could only happen at a Private School.